1. Field of the Invention
The present invention is directed to the field of rolled fingerprint capture, and more specifically, to capturing and combining multiple fingerprint images to generate an overall rolled fingerprint image.
2. Related Art
A rolled fingerprint scanner is a device used to capture rolled fingerprint images. The scanner captures the image of a user's fingerprint as the user rolls a finger across an image capturing surface. Multiple fingerprint images may be captured by the scanner as the finger is rolled. These images may be combined to form a composite rolled fingerprint image. A computer system may be used to create the composite rolled fingerprint image. Fingerprint images captured by a digital camera are generally comprised of pixels. Combining the pixels of fingerprint images into a composite fingerprint image is commonly referred to as pixel “knitting.”
The captured composite rolled fingerprint image may be used to identify the user. Fingerprint biometrics are largely regarded as an accurate method of identification and verification. A biometric is a unique, measurable characteristic or trait of a human being for automatically recognizing or verifying identity. See, e.g., Roethenbaugh, G. Ed., Biometrics Explained (International Computer Security Association: Carlisle, Pa. 1998), pages 1–34, which is herein incorporated by reference in its entirety.
Capturing rolled fingerprints using a fingerprint scanner coupled to a computer may be accomplished in a number of ways. Many current technologies implement a guide to assist the user. These guides primarily come in two varieties. The first type includes a guide located on the fingerprint scanner itself. This type may include guides such as light emitting diodes (LEDs) that move across the top and/or bottom of the scanner. The user is instructed to roll the finger at the same speed as the LEDs moving across the scanner. In doing so, the user inevitably goes too fast or too slow, resulting in poor quality images. The second type includes a guide located on a computer screen. Again, the user must match the speed of the guide, with the accompanying disadvantages. What is needed is a method and apparatus for capturing rolled fingerprint images without the requirement of a guide.
Current devices exist for collecting rolled fingerprint images. For instance, U.S. Pat. No. 4,933,976 describes using the statistical variance between successive fingerprint image “slices” to knit together a composite fingerprint image. This patent also describes techniques for averaging successive slices into the composite image. These techniques have the disadvantage of less than desirable image contrast. What is needed is a method and apparatus for capturing rolled fingerprint images with improved contrast imaging.